The electronic surveillance network Echelon played a key role in the capture of the alleged September 11 mastermind, Khalid Sheikh Mohammed, it was reported yesterday - as did a $27m (£18m) payment to an "al-Qaida foot soldier", who may be planning to relocate to Britain.

The new details of the arrest were emerging as Pakistan's main intelligence agency held an unprecedented briefing on the capture for foreign journalists in Islamabad.

Reporters watched a video that appeared to show Pakistani agents in bullet-proof vests scaling the wall of Mohammed's building, then handcuffing him and placing a black hood over his head.

In an apparent effort to signal their independence from US law enforcement agencies, officials at the briefing stressed that only Pakistani nationals had been involved in Mohammed's arrest in the city of Rawalpindi on March 1.

But Mohammed's face was not shown during the raid - because, the officials claimed, they had too much footage and needed to edit it.

Only at a later stage is he shown at a detention centre, with a blanket wrapped around him. "He had a fever at the time of the arrest," said the officials.

The video also fails to capture the shooting incident that took place at the time of the raid. But during the briefing, the officials disclosed that Mohammed did try to resist arrest, and fired at least one round from an AK-47 assault rifle before surrendering to the authorities. An army colonel was hit in the foot, and is recovering at a military hospital in Rawalpindi.

In Washington, the national security agency used Echelon, an intelligence system coordinated by the United States but involving several of its allies, including the UK, to monitor more than 10 mobile phones used by Mohammed.

"They were tracking him for some time," an unnamed intelligence official told the American news magazine US News and World Report. "He would shift; they would follow."

Echelon reportedly monitors phone numbers and voices, then uses satellite triangulation to locate the user. The Swiss justice ministry has confirmed reports that the September 11 hijackers used pre-paid Swiss cellular phones, not registered in any name and thus hard to trace, in preparing the attack.

"Let's say that thing that drug traffickers and terrorists thought they could do to avoid detection are really not effective strategies anymore," said Larry Johnson, a former deputy director for counter-terrorism at the US state department. "The technology being used now [by the authorities] is really pretty effective."

The rival magazine Newsweek quoted a Middle Eastern intelligence source as saying that an unidentified al-Qaida member "turned over and made a deal with the United States", taking the $25m reward offered and extracting a supplementary $2m in order to relocate with his family to the United Kingdom. A US law enforcement source confirmed that the payment had been made, the magazine said.

Other Pakistani intelligence sources said the real breakthrough had come when the FBI had managed to "persuade" an al-Qaida operative arrested earlier to reveal the whereabouts of Osama bin Laden or his close associates. The man was arrested in Quetta, capital of Baluchistan province, but his identity was never made public.

These sources say the Pakistani officials were kept in the dark about the real identity of this man, or the deal that the American had cut with him. The sources said it was only a few hours before the raid on Mohammed's hideout in Rawalpindi that the FBI had informed Pakistani intelligence, and had asked it to carry out the raid without the help of the local police or the civilian intelligence services.

Though the FBI was not directly involved in the raid to seize Mohammed, it observed the operation from a distance, and got immediately involved in the interrogation process, the sources said.

Officials from Pakistan's Inter-Services Intelligence agency, who could not be named according to the terms of the briefing, said information gleaned from Mohammed was closing the net on Bin Laden. Mohammed claimed to have met Bin Laden in December, an official confirmed, but he had not yet backed up the claim by saying where it took place.

The arrest "is bringing us significantly closer to Osama", one official said. "We appear to be just hours behind him ... Khalid Sheikh said he met with him in December. We were months behind, then weeks, and now hours behind him."

Contradicting earlier reports that Mohammed had stayed in Pakistan only hours after his arrest, the officials said he had remained for three days before being moved to US custody at an undisclosed location, where he remains. Ahmed al-Hawsawi, an alleged financier of the September 11 attacks, was arrested at the same time.

Pakistani security forces yesterday said they had arrested at least two more non-Pakistanis in Peshawar on Saturday on suspicion of affiliations with al-Qaida. A raid took place in an upmarket district of the city, intelligence sources said, resulting in the arrest of an Iraqi Kurd and an Iranian.

Authorities had been led to the address after intercepting phone conversations between al-Qaida leaders, possibly including Bin Laden, and a third man, reportedly an Afghan named Masood.

US forces are understood to be in southern Afghanistan, and in the mountainous border regions between Afghanistan and Pakistan, hunting for Bin Laden and other al-Qaida members.